Australia has seen an increase in the importation and use of drugs that are marketed and sold as “Legal Highs”. These compounds have largely tended to be various cathinone analogues, with 4-methylmethcathinone the most prominent to date. In January 2009, unknown samples were submitted for analysis along with a large seizure of 3-fluoromethcathinone as part of a police operation. The samples were analysed and determined to be 3,5-difluoromethcathinone and 3,5-dichloromethcathinone. These compounds were synthesised and characterised. The GC–MS data of the samples and their N-acetyl derivatives, NMR, vapour-phase and condensed-phase IR for these previously unreported compounds are presented. This analytical data will enable laboratories to confirm the presence of these compounds in the absence of commercially available reference standards.